Method for extruding woven net-like structures



0 'r. H. FAIRBANKS 3,5

METHOD FOR EXTRUDING WOVEN NET-LIKE STRUCTURES Filed Oct. 24, 1967 3snets-sneet 1 Aug. 25, 1970 T. H.-FAIRBANKS ,5

METHOD FOR EXTRUDING WOVEN NET-LIKE STRUdTURES Filed Oct. 24, 1967 4 v 5sheets-s am Aug. 25, 1970 T. H. FAIRBANKS METHOD FOR EXTRUDING WOVENNET-LIKE" STRUCTURES Filed Oct. 24, 1967 3 Sheets-Sheet 5 United StatesPatent 3,525,785 METHOD FOR EXTRUDING WOVEN NET-LIKE STRUCTURES TheodoreH. Fairbanks, West Chester, Pa., assignor to FMC Corporation,Philadelphia, Pa., a corporation of Delaware Filed Oct. 24, 1967, Ser.No. 677,603 Int. Cl. D01d 5/20; D02g 1/20 U.S. Cl. 264-103 v 6 ClaimsABSTRACT OF THE DISCLOSURE A method of making a woven web or braidshaving interlaced strands by periodically crossing a series of extrudedstreams with another series of extruded streams without contacting witheach other.

The invention relates to a method for making woven webs or net-likestructures by extrusion.

U.S. Pat. 2,919,467, is typical of a large number of prior disclosuresrelating to the manufacture of net-like structures by extrusion in whichan integral junction is formed at every intersection of mesh strands.

In accordance with the invention disclosed in my US. patent application6-5 6,501, entitled Manufacture of Net- Like Structures it is nowpossible to make a net-like structure which has the appearance of awoven fabric. In such structure at least some of the individual meshstrands are bonded to certain intersecting strands at their points ofcrossing to form integral, unitary strand junctions, and are unconnectedto other of such intersecting strands at their points of crossing.Completely lacking in prior disclosures are teachings or suggestions formaking a woven net-like web or fabric by direct extrusion. Accordingly,a primary object of this invention is to provide a new or generallyimproved and more satisfactory method for making woven webs or net-likestructures.

Another object of this invention is a method for making woven webs ornet-like structures by extrusion.

Still another object is the provision of a method for extruding braidsor webs having interlaced strands.

A further object is the provision of a method for extruding woven webshaving non-ravelling edges.

A still further object is the provision of a method which is adapted forcontinuous, and economical manufacture of woven webs by extrusion.

These and other objects are accomplished in accordance with the presentinvention by a method in which a series of streams of plastic orflowable strand-forming material are extruded in each of two spaced,generally parallel surfaces. The term surfaces is employed throughoutthe description and claims in its geometrical sense as a two-dimensionallocus of points and thus includes both planes and curved (e.g.cylindrical) surfaces. These streams are moved within the respectivesurfaces transversely of the direction of extrusion and with themovement of the series of streams within one surface being in adirection opposite to that of the series of streams within the other ofsuch surfaces. Thus, the series of extruded streams in one surfaceperiodically cross with the series of streams in the other of suchsurfaces. These crossing streams, however, do not contact with eachother since the surfaces in which they lie are spaced from each other.At locations which alternate with the locations at which the streamscross, the respective series of streams are caused to simultaneouslyreverse or exchange planes along which they are extruded, withoutinterruption in the extrusion of such streams, to effect interlacing ofthe two series of streams. The extruded streams of strand-formingmaterial, in their crossing and interlaced relationship are then set, toprovide a Woven web or netlike structure.

ice

The movement of each series of streams within their respective surfacesis preferably continuous, with the streams of each series moving inunison. This movement of the streams transversely of the direction ofextrusion and the periodic reversal of the surfaces along which therespective series of streams are extruded is preferably effected at thepoints at which such streams are extruded.

Setting .of the extruded streams of flowable strandforming material isachieved in a conventional manner, as .by cooling, solvent removal, orchemical conversion, depending upon the particular character of theStrandforming material which is being employed.

:iThe apparatus for carrying out the above-described method includes apair of movable members, having like sets of extrusion openings therein,which are supported along opposite sides of and in sliding contact witha fixed separator plate having a series of spaced partitions. Means areprovided for feeding plastic or flowable strand-forming material to theopenings in the movable members from which it is extruded in each of apair of spaced parallel surfaces as a series of streams, and for movingthe members so as to displace the openings in one of such members in adirection opposite to the displacement of the openings in the the otherof such members and transversely of the direction of extrusion. Theapparatus further includes means for periodically causing the series ofstreams to simultaneously reverse surfaces along which they are extrudedso as to provide for interlacing of such strands.

The separator plate is positioned between the movable members with thefree ends of the spaced partitions thereof terminating adjacent to theexit portions of the openings in the movable members, and preferablyextending slightly beyond the exit portions of such openings. The spacebetween the movable members which is occupied by the partitions isclosed by a portion of the separator plate which extends along andadjacent to entrance portions of the openings in such movable members sothat the only material which is extruded is that which is delivered tothe openings in the movable members. The partitions of the separatorplate are only of such thickness as to satisfy strength requirements.

More specifically, in one illustrated embodiment the apparatus includesa pair of elongated, parallel, rollers which are supported alongopposite sides of and in sliding contact with the fixed separator plate.The rollers are of like construction, with each having peripheralgrooves located at spaced intervals along intersecting helices of thesame pitch. All of the grooves are of the same length and each is equalin length to the ungrooved portion of the roller surface extendingbetween the ends of adjacent grooves of the same hand. Morespecifically, the ends of each groove and the ends of adjacent groovesalong either helix are spaced the same distance, as measured along thelength of the roller. While these grooves extend along intersectinghelices, the grooves of one hand are located so as to pass midwaybetween the ends of adjacent grooves of the opposite hand. All of theroller grooves are also of like width and are at least as wide at theroller periphery as they are at their base to insure easy removal ofplastic material therefrom.

The separator plate is of a construction as heretofore mentioned, withthe spaces or slots between partitions having a center-to-center spacingequal to the length of each roller groove, as measured along the lengthof the roller. The Width of each of these slots of the separator plateis substantially equal to the width of the roller grooves and thus thepartitions are each of a width equal to the length of a roller groove,as measured along the length of a roller, less the width of a separatorplate slot.

As heretofore mentioned, the separator plate is fixed and thus remainsstationary. The rollers, however, are

both turned so that the grooves therein cooperate with the stationaryseparator plate to define extrusion orifices. Plastic material which isto be extruded is delivered under the pressure to the side of therollers opposite the free ends of the partitions of the separator plateand thus flOtWS through the extrusion orifices, as defined by theseparator plate and the grooves in the rotating rollers, and toward thefree ends of the separator plate partitions.

Since each of the roller grooves extends along a helix, the extrusionorifices defined by such grooves and the streams of plastic materialissuing therefrom will travel transversely of the direction of extrusionas the rollers are turned, either in the same or opposite directions,Thus, if the rollers are both to be turned in the same direction, thegrooves of the two rollers which, at any moment define extrusionorifices, extend along helicesbf opposite hand so that the streamsissuing therefrom travel in opposite directions transversely of thedirection of extrusion. On the other hand, if the rollers are to berotated in opposite directions, the extrusion orifices are defined, atany particular moment, by grooves extending along corresponding helicesof the same hand on the two rollers, so that the transverse travel ofthe streams extruded from orifices defined by the grooves of one of therollers will be opposite to that of the streams extruded from orificesdefined by the grooves of the other of such rollers.

Regardless of the direction of roller rotation, it is essential forsatisfactory practice of the method with this embodiment that extrusionof plastic material through the orifices commence when the leading endsof the grooves defining such orifices are aligned with spaces betweenseparator plate partitions and terminate when the opposite or trailingends of such grooves move into alignment with spaces between partitionsimmediately adjacent those at which extrusion was started.

In the operation of the specific embodiment described above, streams ofplastic material as described above, will be extruded through orificesdefined by grooves extending along helices of unlike or like hand,depending upon the direction of roller rotation. The helical grooveswill cause the extruded streams to move transversely of the direction ofextrusion, with the transverse movement of the series of streamsextruded from grooves of one roller being in a direction opposite to theseries of streams issuing from grooves of the other of such rollers. Thestreams of one of the series of streams will alternate with the streamsof the other thereof and, as such series of streams undergo theiropposite movement transversely of the direction of extrusion, adjacentstreams will pass each other or cross about midway of adjacent separatorplate partitions. The partitions, however, will maintain such streamsseparated from each other at these locations so that bonding of thecrossing streams will be prevented.

With continued roller rotation, the roller grooves through which plasticmaterial is extruded approach and then move into alignment With slots inthe separator plate. Full communication with slots in the separatorplate is achieved at the trailing ends of such grooves. Simultaneouslywith the movement of the trailing ends of these grooves into alignmentwith slots in the separator plate, the leading ends of grooves in anopposing roller also move into alignment and communication with theseparator plate slots. Thus, as extrusion of plastic material fromcertain roller grooves stops, extrusion concomitantly starts throughgrooves of an opposing roller which are aligned therewith and, sincesuch aligned grooves communicate with each other through the separatorplate slots, continuity of the extruded streams is maintained.

The result of extruding a separate series of streams of plastic materialthrough grooves of each of the rollers and the continuation of extrusionof the streams of the respective series through grooves of an opposingroller, as described above, is that the respective series reverse orexchange surfaces or planes along which the streams thereof areextruded. As wvill be more apparent hereafter, this movement of streamsfrom one plane to another pro vides for interlacing of the streamswhich, when set, result in a desired pattern of woven strands.

Of significance in this reversal or exchange of planes along which theseries of streams are extruded is that the roller grooves through whichextrusion of plastic material is terminating and the roller grooves ofan opposing roller through which extrusion is simultaneously startingare of opposite hand if the rollers are rotating in the oppositedirections or of the same hand if the rollers are rotating in the samedirection. That is, the roller rotation containing the latter grooveswill be such that the individual strands will at all times continue tomove in the same direction during their travel transversely of thedirection of extrusion.

In the embodiment thus far described, it is preferred that the rollergrooves which extend along intersecting helices terminate, adjacent tothe ends of the rollers, in grooves which extend annularly about theroller peripheries. These annular grooves are at all times in alignmentwith solts in the separator plate so that straight streams of plasticmaterial are continuously extruded therefrom. Since certain of theroller grooves which extend along intersecting helices terminate orconnect with these annular grooves, it will be apparent that thestraight, continuous streams of plastic material extruded from thelatter grooves will serve, when set, as selvage strand which maintainthe interlaced relationship of the other strands of the resultingstructure or web and thus prevent the same from unravelling.

In addition to or as an alternative to annular roller grooves asdescribed above, the opposite end portions of both rollers may beprovided with grooves along all of the intersecting helices. Streamsextruded through the roller grooves on opposite sides of the separatorplate partitions would contact each other at the separator plate slotsto form integral junctions which would firmly hold the woven strands inthe relative positions and provide for a somewhat elastic selvage alongthe resulting Web.

It will, of course, be apparent that some variation can be made instructure and operation of the above-described apparatus Withoutdeparting from the spirit and scope of the invention. For example, thenumber or pitch of the grooves along each helix may be changed,providing each helix has the same number of like grooves. Further, therollers may be of different diameters and thus be driven at differentspeeds as long as the grooves in all rollers extend along helices oflike pitch. Additionally, plastic material of different color and/orcomposition may be extruded through the grooves of the two rollers sothat the color and/ or composition of the interlaced strands differs atintervals along their lengths.

In another embodiment of the present invention, the apparatus includes apair of opposing elongated movable members having sets of cooperating,complementary extrusion openings or grooves formed along opposingsurfaces thereof and to which fiowable, plastic material is delivered. Afixed separator plate, having a construction as heretofore described, ispositioned between the movable members, with the opposing surfaces ofsuch members being in snug but sliding contact with the separator platepartitions. Means are provided for relatively displacing these members,such as by oscillating or reciprocating the same longitudinally inopposite directions.

A shutter is mounted on each side of the separator plate, adjacent tothe free ends of the partitions thereof, for reciprocating movement.Both shutters are shifted in opposite directions through one-half oftheir stroke intermittently and independently of and relative to themovable members, to cause the series of streams of plastic materialextruded through openings in the respective movable members to reverseor exchange planes along which they are extruded.

The elongated .movable members are of like construction, with theextrusion openings or grooves formed along the opposing surfaces thereofbeing of substantially the same width and depth and spaced equaldistances along the length of such members. In the separator plate, thewidth and spacing of the slots or spaces between adjacent partitionscorresponds to that of the openings in the movable members and thus thepartitions themselves are each equal to the center-to-center spacing ofthe extrusion openings less the width of one of such openings.

The shutters are preferably in the form of flat plates having spacedrecesses along the opposing edges thereof. The shutter recesses and theunrecessed portion therebetween are all of the same length, which isequal to the center-to-center distance between adjacent extrusionopenings. The depth of these recesses must be at least equal to depth ofthe openings or grooves in the movable members. As heretofore mentionedthe shutters are mounted for simultaneous reciprocating movement inopposite directions and relative to the movable members.

During extrusion of the streams, the movable members are continuouslyreciprocated at the same speed, with each travelling a distance equal tothe center-to-center spacing of the extrusion openings during one-halfof its stroke. The shutters are positioned with the recesses thereofbeing in aligned relationship and are shifted only at the instant thatthe movable members complete travel in their respective directions andare to reverse their directions of movement. During each shift of theshutters they move in opposite directions, a distance equal to onlyone-half of their reciprocating stroke, which is equal to that of themovable members.

With the movable members in motion as described above and with plasticmaterial supplied thereto, streams of plastic material are extruded fromthose openings of each movable member which travel along recesses in theshutters. The remaining openings in the movable members will be coveredat their exit ends by unrecessed portions of the shutters so that noplastic material issues therefrom. The stream-s extruded throughopenings in the respective movable members will all lie in the samesurface or plane and the series of streams of one series will alternatewith the streams of the other of such series.

The linear motion of the movable members will cause the extruded streamsto travel transversely of the direction of extrusion and, since thesemembers are moved in opposite directions, the streams of one series willcross the streams of the other series as opposing extrusion openings areabout midway across separator plate partitions. At such locationsopenings in the opposing movable members are in aligned relationship butdo not communicate with each other in view of the interposed separatorplate partitions and thus no contact of the crossing streams occurs.

Upon continued travel of the movable members, the openings thereofthrough which plastic material is being extruded approach and then moveinto alignment with slots in the separator plate. These particularextrusion openings also approach unrecessed portions of the stationaryshutters and are each about one-half covered by such portions of theshutter when they are in full communication with the slots in theseparator plate.

As openings in the movable members through which plastic material isbeing extruded move into alignment with separator plate slots, openingsin an opposing movable member, which have heretofore been covered by theunrecessed portions of shutters, also move into alignment andcommunication with the separator plate slots. Moreover, these latteropenings, when in complete communication with the separator plate slots,move partially beyond the unrecessed portions of the shutters and areeach about one-half covered by such shutter portions. Thus, as theunrecessed portions of the shutters partially close off extrusionthrough certain extrusion openings in the movable members, partialextrusion is concomitantly started through openings which are alignedand in communication therewith.

In the position of the elements of the apparatus described above, themovable members are ready to reverse their directions of travel and itis at this instant that the shutters are simultaneously shifted inopposite directions to now locate unrecessed portions thereof overopenings in the movable member which had just previously travelled alongshutter recesses and to completely open extrusion openings which are inalignment therewith. Concomitantly with this shifting of the shuttersthe movable members reverse their directions of travel. Extrusion ofplastic material is continuous and upon shifting of the shutter asdescribed above, openings in the movable members which had previouslybeen covered by the unrecessed shutter portions now travel alongrecesses in the shutter so that continuous streams issue therefrom. Onthe other hand, openings in the movable members through which extrusiondid occur prior to the reversal of travel of such member, now moverelative to unrecessed shutter portions and are thus covered at theirexit ends.

The result of extruding a separate series of streams of plastic materialthrough openings or grooves in each movable member and the continuationof extrusion of the streams of the respective series through grooves ofan opposing movable member, as described above, is that the respectiveseries reverse or exchange planes along which the streams thereof areextruded. As will be more apparent hereafter, this movement of streamsfrom one plane to another provides for interlacing of the streams which,when they are set, result in a desired pattern of woven strands.

Of significance in this reversal or exchange of planes along which theseries of streams are extruded is that the openings in a movable memberthrough which extrusion of the plastic material is terminating andopenings in an opposing movable member through which extrusion issimultaneously starting are moving in opposite directions transverselyof the direction of extrusion. As a result, the individual strands will,at all times (that is, both before and after movement into and out fromthe different planes of extrusion) continue to move in the samedirection during their travel transversely of the direction ofextrusion.

After the shift of the shutters, the movable members continue theirmovement in reverse directions until opposing openings in such membersagain cross and are in alignment with separator plate slots. In thislatter position the planes along which the streams are extruded areagain reversed as described above.

In this embodiment, the rate of extrusion and/0r reciprocation of thedisplacea'ble members may be varied, providing the movement of theshutters is also changed accordingly, and plastic material of differentcolor and/ or composition may 'be extruded through the openings of theseparate displaceable members.

Throughout the disclosure, the terms align and alignment mean thejuxtaposition of extrusion openings of the respective sets in theirdisplacement so as to coincide or come exactly opposite to one anotheror into partially over-lapping positions. The term communication, alsoas employed with the sets of extrusion openings, means that alignedopenings are open to each other at a slot in the separator plate so thatthey together form a single composite opening.

While the following detailed description of the second embodiment makesreference to elongated or flat movable members, the teachings of thisinvention are equally applicable to annular movable members andcorrespondingly shaped shutters which can be relatively displaced withoscillating movements.

The teachings of the present invention are applicable for use with avariety of materials, which are referred to by the term plastic,including materials which are thermoplastic, such as polyamides orsuperpolyamides, polyesters, polyvinyl chloride, copolymers thereof,polyolefins, cellulose acetates, metals, glasses, etc., natural orsynthetic rubbers, thermo-setting materials or wet-spinnable materials,such as viscose, cupro-ammonium cellulose, or carboxymethyl cellulose.Such materials may include various additives such as stabilizers, dyes,foaming agents, etc., if so desired. It will be apparent that the mannerby which the extruded junction and mesh-strand forming streams are setwill depend upon the particular material which is being employed.

For a greater understanding of this invention, reference is made to thefollowing detailed description and drawing in which FIG. 1 is a verticalsection taken transversely of one embodiment of apparatus employed inthe method of the present invention;

FIG. 2 is a perspective view of a portion of the apparatus shown in FIG.1;

FIG. 3 is a diagrammatic view illustrating the woven pattern of thenet-like structure which is produced by the apparatus shown in FIG. 1;

FIG. 4 is a diagrammatic view illustrating a portion of a woven net-likestructure having a modified edge section;

FIG. 5 is a view similar to FIG. 4 showing a portion of a woven net-likestructure having a still further modified edge section;

FIG. 6 is a vertical section taken transversely of a second embodimentof apparatus employed in the method of the present invention;

FIG. 7 is a bottom view of a portion of the apparatus shown in FIG. 6;

FIG. 8 is a diagrammatic view illustrating the woven pattern of thenet-like structure which is produced by the apparatus shown in FIG. 6;and

FIG. 9 is a view illustrating the same elements of the apparatus shownin FIGS. 6 and 7, in various positions, designated as A, B, C, D, E andF, assumed during the production of the fabric shown in FIG. 8.

With reference to the drawing, the apparatus shown in FIG. 1 is designedfor making a woven net-like structure or fabric from thermoplasticmaterial and includes an elongated extrusion block having a chamber 17,into which molten thermoplastic material is delivered as by aconventional screw extruder, not shown, the block 15 has suitable endplates and a discharge slot 19. Positioned within and extending thelength of the chamber 17 is a rigid bar 21 which is fixed in place bypins 23. A separator plate 25 is supported and extends from the bar 21and projects through the slot 19 and in between a pair of rollers 27 and29. The lower end of the extrusion block 15 is suitably shaped withcurved walls 31 for receiving the rollers 27 and 29 which, together withthe separator plate 25 close the discharge slot 19.

The rollers 27 and 29 engage snugly with the opposite sides of theseparator plate 25 and are each provided with spindles 33 which projectfrom opposite ends thereof. The roller spindles 3-3 are supported bysuitable means, not shown, so as to permit the rollers 27 and 29 toturn. As heretofore mentioned, the rollers 27 and 29 may be rotated inthe same or opposite directions and for the sake of simplicity arehereafter described as being rotatable in opposite directions, asindicated by arrows 35 and 37 respectively.

As shown in FIGS. 2 and 3, the roller 27 is formed with grooves 39, 41and 43 extending along one helix, as indicated by line 45, and grooves47 and 49 extending along another helix, as indicated by line 51, whichis of opposite hand and thus intersects with the helix 45. The helicesand 51 are of like pitch and the grooves are oriented so that thegrooves extending along one helix, such as the grooves 39, 41 and 43,pass midway between the ends of the grooves formed along theintersecting helix, such as grooves 47 and 49. All of the grooves in theroller 27 are of the same length and are equal in length to theungrooved portion of the roller surface extending between the ends ofadjacent grooves of the same hand.

More specifically, in the construction illustrated, the ends of eachgrooves and the ends of adjacent grooves along either helix are spacedthe same distance, as measured along the length of the roller 27;namely, one-half of the helix pitch. The grooves 39, 41, 43, 47 and 49are of like width and are of substantially the same width throughouttheir depth.

The roller 29 is of the same construction as the roller 27, havinggrooves 53, 55 and 57, which correspond to grooves 39, 41 and 43 of theroller 27, extending aong a helix denoted by line 59 and grooves 61 and63, corresponding to grooves 47 and 49 of the roller 27, extending alonga helix as indicated by line 65.

In addition to the helical grooves described above, annular grooves 67and 69 are provided in the roller 27 and are aligned with similarannular grooves 71 and 73 formed in the roller 29. As shown in FIG. 2,the ends of the outermost helical grooves of each roller, such as thegrooves 39 and 43 of the roller 27, merge with or connect with theannular grooves which are adjacent thereto.

As shown in FIGS. 1 and 2, the free edge of the plate is slotted at 75to provide partitions 77. The free ends of the partitions 77 terminatebelow a plane passing through the centers of the rollers 27 and 29, andthe space between the rollers 27 and 29 which is occupied by the slots75 and partitions 77 is closed by a portion of the separator plate sothat the only material which is extruded is that which passes throughthe roller grooves. The slots 75 in the separator plate aresubstantially equal in width to the grooves in the rollers 27 and 29 andhave a center-to-center spacing equal to the length of a roller grooveor, in the construction illustrated, equal to onehalf, of the pitch ofthe helices along which the grooves extend.

In the described apparatus, the rollers 27 and 29 are oriented as shownin FIG. 2 so that the leading ends of grooves formed along thecorresponding helices of the two rollers, such as the grooves 39, 41 and43 of the roller 27 and grooves 53, 55 and 57 of the roller 29, will besimultaneously aligned with slots 75 in the separator plate duringrotation of the rollers.

With the parts of the apparatus in positions as shown in FIGS. 1 and 2,the rollers 27 and 29 are together rotated continuously and at the samerate of speed in the direction of arrows 35 and 37, respectively, bysuitable means, not shown. Molten thermoplastic material is deliveredinto the chamber 17, passes through the slot 19 and is received incertain of the roller helical grooves as well as the annular grooves 67,69, 71 and 73. For example and more particularly, molten thermoplasticmaterial received in the grooves 39, 41 and 43 of the roller 27 iscarried away from the slot 19 as such roller is turned in the directionof arrow 35 and issues from the apparatus as continuous streams, whichare indicated at 79, 81 and 83 in FIG. 3. Since these grooves extendhelically about the roller 27, the points at which extrusion Occurs fromthe respective roller grooves will move transversely of the direction ofextrusion as the roller 27 is turned. More specifically, as viewed inFIG. 2, clockwise rotation of the roller 27 will cause the streams 79,81 and 83 which are extruded from the roller grooves 39, 41 and 43 tomove toward the observer.

Simultaneously, molten thermoplastic material will also be received inthe grooves 53, 55 and 57 of the roller 29 and, as this roller is turnedin the direction of arrow 37, will issue therefrom as continuousstreams, which are as indicated at 35, 87 and 89 in FIG. 3. The grooves53, 55 and 57, of the roller 29 also extend along helical paths and thusthe points at which the streams 85, 87 and 89 are extruded will movetransversely of the direction of extrusion, or away from the observer asviewed in FIG. 2, with counterclockwise rotation of the roller 29.

As the grooves 39, 41 and 43 of the roller 27 and the grooves 53, 55 and57 of the roller 29 move half way across a common partition 77 and arethus aligned with each other, the streams issuing therefrom will cross,but will not contact each other since the partitions themselves maintainthe streams separated from each other. With continued rotation of therollers 27 and 29, the trailing ends of the grooves 39, 41 and 43 in theroller become aligned and communicate with alternate slots 75 in theseparator plate 25. More specifically, the trailing end of the rollergroove 39 will become aligned with the separator plate slot 75 nearestto the observer, as viewed in FIG. 2, through which the annular grooves67 and 71 of the rollers 27 and 29, respectively, are maintained incontinuous communication with each other. A continuous straight orvertical stream of thermoplastic material, indicated at 91 in FIG. 3, isextruded from the aligned annular grooves 67 and 71 of the rollers 27and 29 and, since the roller groove 39 opens into the annular groove 67,the thermoplastic material issuing therefrom will terminate at and blendinto the stream 91 as shown at 93.

At alternate slots 75 in the separator plate 25, the trailing ends ofthe grooves 41 and 43 of the roller 27 will align and communicate withthe leading ends of grooves 61 and 63 of the roller 29. At this time,extrusion of thermoplastic material through the grooves 41 and 43 in theroller 27 ceases and simultaneously commences through the grooves 61 and63 in the roller 29. Thus, the streams 81 and 83, being first extrudedfrom the left side of the separator plate 25, as viewed in FIG. 2, arenow extruded from the right side thereof.

concomitantly, with the movement of grooves 39, 41 and 43 of the roller27 into alignment with separator plate slots 75, the grooves 53, 55 and57 of the roller 29 are also aligned with slots 75 in the separatorplate 25. More particularly, the roller groove 57 becomes aligned withthe separator plate slot 75 furthest away from the observer, as viewedin FIG. 2, through which the annular grooves 69 and '73 of the rollers27 and 29 are maintained in continuous communication with each other. Astraight or vertical stream of thermoplastic material, indicated at 95in FIG. 3, is extruded from these aligned annular grooves 69 and 73,and, since the roller groove 57 opens into the annular groove 73, thethermoplastic material issuing therefrom will terminate at and blendwith the stream 95, as indicated at 97.

At the same time, the trailing ends of the grooves 53 and 55 will becomealigned with slots 75 in the separator plate 25, which alternate withthe slots 75 aligned with the grooves 41 and 43 of the roller 27, andwill communicate with the leading ends of grooves 47 and 49 in theroller 27. In this position, extrusion of thermoplastic material fromthe grooves 53 and 55 stops and simultaneously starts to issue from thegrooves 47 and 49, Thus, the streams 85 and 87, being first extrudedfrom the right side of the separator plate are now extruded from theleft side thereof.

The above-described exchange or reversal of planes of extrusion of thestreams provides for interlacing of the streams below the extrusionapparatus, as indicated at 99. The streams of thermoplastic material 81and 83 now being extruded from the grooves 61 and 63 of the roller 29and the streams 85 and 87 extruded from the grooves 47 and 49 of theroller 27 are moved relative to the partitions 75 of the separator plateand transversely of the direction of extrusion. Of significance is thatthe respective streams issue first from grooves of one roller and thenfrom grooves of opposite hand in an opposing roller and thus maintaintheir original direction of transverse movement relative to thedirection of extrusion.

In a manner as heretofore described, the streams of thermoplasticmaterial extruded from the grooves 47 and 49 of the roller 27 and thegrooves 61 and 63 of the roller 29 cross each other without contactingas the opposing grooves pass each other during their travel half wayacross common partitions of the separator plate. As such grooves againalign themselves with slots 75 in the separator plate, the streams againexchange or reverse planes of extrusion, as heretofore described. Thestreams of molten thermoplastic material, which are extruded may bequenched, as by cool air, to provide a desired fabric or net-likestructure of interwoven strands.

If desired, the above-described apparatus may be modified to provide theend portions of both rollers with grooves along all of the intersectinghelices. The annular roller grooves 67, 69, 71 and 73 may be retained,in which case the grooves at the end portions of the rollers wouldterminate therein, or such annual grooves may be eliminated. Streamswould be extruded on opposite sides of the separator plate as therollers are turned. These streams would contact each other at theseparator plate slots to form integral junctions. The resulting webwould have edge portions as illustrated in either FIG. 4 or 5, thelatter being formed by rollers having no annular grooves.

Referring now to the embodiment shown in FIGS. 6-9, the a paratus thereillustrated includes an elongated extrusion block having a chamber 107into which molten thermoplastic material may be delivered, as by aconventional screw extruded not shown. A pair of guides 109 and 111 arefixed by bolts 113 to the extrusion block 105 and are each formed with arib or rail 115 Which together support flat movable members 117 and 119for sliding movement. More particularly, the ribs or rails 115 of theguides 109 and 111 are received in grooves 121 formed in the movablemembers 117 and 119 so that the latter are adapted to be movedtransversely of the direction of extrusion as well as in .directionstoward and away from each other.

Both the pair of guides 109 and 111 and the movable members .117 and 119are formed with opposing converging surfaces, as indicated at 123 and125, which extend the length thereof and altogether provide a cavity 127which receives the molten thermoplastic material from the chamber 107. Aset of like spaced grooves or openings are formed in the opposingsurfaces of the movable members 117 and 119. For the sake of simplicityand ease of description, the grooves in the movable members 117 and 119have been designated in FIG. 9 by capital and lower case lettersrespectively. Means, not shown, are provided for reciprocating themovable members .117 and 119 so that the sets of spaced grooves in suchmembers are periodically aligned with each other.

Positioned within and extending the length of the cavity 127 is a rigidbar 129 which is fixed by pins 131. A separator plate 133 is supportedby and extends from the bar 129 and projects in between the movablemembers 117 and 119. The opposing surfaces 135 of the movable membersare maintained in snug but slidable contact with the sides of the plate133, as by adjusting screws 137 which extend through the guides 109 and111 and abut against the die-carrying members.

As shown in FIGS. 6 and 7, the free edge of the plate 133 is slotted at139 to provide partitions 141 which preferably extend beyond theoutermost surfaces 143 and 145 of the movable members 117 and 119. Theslots 139 in the plate 133 are of the same width and spacing as thegrooves formed in the opposing surfaces of the. movable members 117 and119 and open into the cavity 177. The partitions 141 serve to preventthe grooves in the movable members 117 and .119 from communicating witheach other in certain of their aligned positions. As heretoforementioned, the plate 133 is preferably made as thin as permitted bystrength requirements.

A pair of shutters 147 and 149 are supported by guides 151 for slidablemovement along opposite sides of the plate 133 and relative to themovable members 117 and 119. A pair of cranks .153, each acting throughlinks 155 and 157, serve to reciprocate the shutters 147 and 149 inopposite directions at selected time intervals. Screws 159 fixed to themovable members 117 and 119, and extending through slots 161 in theshutters, prevent opposing 1 1 edges of such shutters from moving awayfrom the members .117 and 119 under extrusion pressures.

Recesses 163 occur along the opposing edges of the shutters 147 and 149.The recesses 163 and the unrecessed portions 165 therebetween are all ofthe same length wh ch is equal to the center-to-center spacing of thegrooves formed along opposing surfaces of the members 117 and 119. Thedepths of each of the shutter recesses 163 are at least equal to thedepth of the grooves in the movable members.

In the operation of the above-described apparatus, molten thermoplasticmaterial is delivered through the chamber 107 and into the cavity 127.With the elements of the apparatus initially positioned as illustrated,for example, in FIG. 9A, the members 117 and 119 are moved at the samerate of speed in opposite directions, as shown by arrows .167 and 169,relative to the fixed separator plate 133 and the shutters 147 and 149.During this movement, grooves S, U, W and Y in the member 117 willtravel along recesses 163 in the shutter 147 and molten material willissue therefrom as streams 171, 173, 175 and 177, as shown in FIG. 8.Likewise, grooves t, v, and x in the member 119 will travel alongrecesses 163 in the shutter 149 so that molten material will issuetherefrom as streams indicated at 179, 181 and 183 in FIG. 8.

The remaining of the illustrated grooves in the members 117 and 119 willtravel relative to and be covered by the unrecessed portions 165 of theshutters 147 and 149 and thus no thermoplastic material will issuetherefrom. Midway of their movement along the shutter recesses 163, thegrooves U, W and Y in the member 117 and the grooves t, v and x in themember 119 will be in aligned positions, as shown in FIG. 9B. Thepartitions 141 of the separator plate 133 will, however, be interposedbetween such grooves so that no contact and bonding of the separatelyextruded streams occurs.

With continued movement in the direction of arrows 167 and 169, opposinggrooves in the members 117 and 119 are aligned with slots 139 in theplate 133 and are thus in communication with each other, as shown inFIG. 9C. Grooves U, W and Y in the member 117 and grooves t, v and x inthe member 119 have completed their travel along the shutter recesses163 and are now partially covered by unrecessed portions 165 of theshutters so that extrusion of molten thermoplastic material therethroughis reduced. Likewise, grooves T, V, and X in the member 117 and groovess, u, w and y in the member 119 have completed their travel along theunrecessed portions of the shutters and extend partially into recessesthereof so that extrusion has started therethrough. Thus, whileextrusion of molten thermoplastic material is reduced through certain ofthe grooves of the members 117 and 119, extrusion is started in grooveswhich are aligned and in communication therewith so that continuity ofthe streams is maintained.

At the instant the members move into positions as illustrated in FIG.9C, the shutters 147 and 149 are shifted in opposite directions asindicated by arrows 185 and 187 in FIG. 9D. It will be noted that theshutters are moved a distance equal to the spacing between grooves inthe movable members 117 and 119.

Simultaneously with the shifting of the shutters 147 and 149, themovable members 117 and 119 each reverse their direction of travel asindicated by arrows 189 and 191, with the members 117 and 119 moving inopposite directions to the respective shutters 147 and 149. As a result,grooves U, W and Y in the member 117 and grooves t, v and x in themember 119, through which extrusion of thermoplastic was reduced, areprogressively and then completely covered by unrecessed portions 165 ofthe shutters 147 and 149. concomitantly, grooves T, V and X in themember 117 and grooves s, u, w, and y in the member 119, through whichextrusion of thermoplastic material has been initiated, areprogressively un- 12 covered until they assume positions completelywithin recesses 163 of the shutters 147 and 149.

It will be noted that the concomitant shifting of the shutters andreversal in the direction of movement of the members 117 and 119 causesthe streams of thermoplastic material to exchange or reverse planesalong which they are extruded. Of significance is that while theindividual streams of thermoplastic material are extruded from groovesof one movable member and then from grooves of the other of such member,the members themselves reverse their directions of travel as the streamsexchange or reverse planes of extrusion and thus the individual streamsat all times move in the same direction transversely of the direction ofextrusion.

As shown in FIG. 9B, grooves in the members 117 and 119 are in alignedbut non-communicating relationship as they travel midway across theshutter recesses, thus causing the streams extruded therefrom to crossbelow the extrusion apparatus, as indicated at 193. This crossing of theextruded streams of thermoplastic material is similar to that achievedwhen the elements of the apparatus are in positions illustrated in FIG.9B, with the exception that the streams, having exchanged planes ofextrusion, cross on opposite sides of each other.

With continued movement in the direction of arrows 189 and 191, themembers 117 and 119 reach positions as shown in FIG. 9F, whereupon theshutters 147 and 149 are shifted in the direction of arrows and 197respectively, and the members 117 and 119 themselves reverse theirmotions and again travel in the direction of arrows 167 and 169. Thismovement again results in an exchange or reversal of planes along whichthe streams of thermoplastic material are extruded, in a manner asheretofore described. The extruded streams of thermoplastic material areset, as by cooling, below the extrusion apparatus and it can be seenthat by continuously repeating the above sequence of steps the fabric ornet-like structure which results consists of strands interlaced witheach other into a woven construction.

It is to be understood that changes and variations may be made withoutdeparting from the spirit and scope of the invention as defined in theappended claims.

I claim:

1. A method of making a woven web by extrusion including the steps ofcontinuously extruding a series of spaced streams of a flowablestrand-forming material selected from the group consisting ofpolyamides, polyesters, polyvinyl chloride, polyolefins, celluloseacetates, metals, glasses, natural rubbers, viscose, cupro-ammoniumcellulose, and carboxymethyl cellulose in each of two spaced surfaces,moving the streams along the respective surfaces transversely of thedirection of extrusion, with the streams in one surface moving in adirection opposite to the streams in the other of such surfaces wherebythe streams in one surface cross with the streams in the other of suchsurfaces without contacting with each other, at locations whichalternate with locations at which the streams cross causing the twoseries of streams to simultaneously exchange surfaces along which thestreams thereof are extruded, continuously repeating the above sequenceof steps and setting the extruded crossing streams while they remain outof contact with each other to provide a woven pattern of strands.

2. A method as defined in claim 1 wherein the exchange of individualstreams of the respective series thereof from one surface to the otheris achieved by concomitantly extruding contacting portions of suchindividual stream in each of the two surfaces, stopping the extrusion ofsuch stream in the one surface and continuing the extrusion of the sameentirely within the other of such surfaces.

3. A method as defined in claim 2 wherein the extrusion of theindividual streams is gradually reduced in the one surface andconcomitantly increased gradually in the other of such surfaces untilthe individual stream is extruded entirely within the other of suchsurfaces.

4. A method as defined in claim 1 wherein the streams in the respectivesurfaces are moved continuously and in unison.

5. A method as defined in claim 1 wherein the movement of the streams inthe respective surfaces and the exchange of surfaces along which thestreams of the respective series are extruded is effected at theirpoints of extrusion.

6. A method as defined in claim 1 wherein the outmost streams in atleast one of the surfaces are extruded as continuous straight streamsand are bonded with streams which are moved into Contact therewith.

References Cited UNITED STATES PATENTS 2,797,728 7/1957 Slaytor et a1.3,029,174 4/1962 Schultheiss.

JULIUS FROME, Primary Examiner I. H. WOO, Assistant Examiner US. Cl.X.R.

